I've been in the pet door business since the late 90s, the Pet Door Store was started in 2003, and one problem that has lingered in this space for all of that time was the lack of a fire rated pet door. FireSafe Pet Doors has solved this problem with their UL certified fire proof doggy door.
The inside frame and pet door is pretty standard; a vinyl flap with a magnet strip to hold it shut, ABS plastic locking cover, powder coated aluminum frame. What makes this one different is the galvanized exterior frame and the fire proof cover. The frame has two rails that hold the cover up above the pet door flap, and it always stays in this position until there is a fire.
In the event of a fire, there is a fusible link which melts, releasing the cover. The cover slides down in its track and seals around the perimeter of the frame melt and seal to it, creating a smoke proof barrier. This product is UL certified for 20 minutes of direct fire exposure.
If you are installing a pet door to the garage, this is really the only option to consider as it is the only fire rated pet door at this time.
If you have installed a cat door so that you can put your litter box in the garage, you can retrofit this door and regain compliance with building codes. This is important for several reasons: 1) if there was a fire in the garage that spread to the rest of the house, and you didn't have a fire rated door, the insurance company may be able to reject a claim on the basis that the fire barrier was breached. 2) Building codes are there to protect you and your family. 3) If you are going to sell your home, this will come up on a home inspection and could be a reason to back out of the sale or reduce the purchase price.